Field of the Invention
The present invention relates to a medical image system and an image processing device.
Description of the Related Art
X-ray equipment, such as Talbot interferometers and Talbot-Lau interferometers, that utilizes the Talbot effect has been known. The Talbot effect refers to a phenomenon of coherent light, which has passed through a first grating having slits formed at regular intervals, forming a lattice image of the first grating in regular cycles in the light traveling direction. The lattice image is called a self-image. A Talbot interferometer or a Talbot-Lau interferometer has a second grating disposed at a position where the self-image is formed, so as to measure interference fringes generated by slightly shifting the second grating. Since moires are distorted by an object placed before the second grating, in order to conduct radiographing using a Talbot interferometer or a Talbot-Lau interferometer, a subject may be placed before the first grating and irradiated with coherent X-rays, and the resulting moire fringe images may be computed so as to obtain a reconstructed image (an absorption image, a differential phase image, or a small-angle scattering image) of the subject.
Note that, if moire fringe images are radiographed with X-ray equipment having a Talbot interferometer or a Talbot-Lau interferometer as described above and the moire fringe images are simply reconstructed, image unevenness caused by a grating used therein is contained in the reconstructed image.
In order to attenuate the image unevenness, correction (hereinafter referred to as a BG process) is conducted in such a manner that a subject reconstructed image generated on the basis of subject moire fringe images acquired by radiographing a subject is subtracted or divided by a background reconstructed image (a BG reconstructed image) generated on the basis of background moire fringe images (hereinafter referred to as BG moire fringe images) acquired by radiographing without placing a subject (hereinafter referred to as background radiographing or BG radiographing.
Since, however, the X-ray spectra of X-rays passing through the subject change, image unevenness caused by the first grating or the second grating also remain in the corrected absorption image or small-angle scattering image resulting from the BG process.
Thus, JP 2014-135989 A, for example, discloses conducting BG radiographing with a homogeneous member that causes the same X-ray spectral change as that caused by X-rays passing through the subject, and performing the BG process by using a BG reconstructed image generated on the basis of the resulting BG moire fringe images, so as to reduce image unevenness remaining in the subject reconstructed image due to the change in the X-ray spectra.
With the technique of JP 2014-135989 A, however, BG radiographing needs to be conducted with a member causing an X-ray spectral change equivalent to that caused by the subject or such radiographing needs to be conducted in advance, which is more troublesome and complicated than the BG radiographing of the related art.